Various types of display device for vehicle have been proposed. Such a conventional display device for vehicle displays a virtual image by projecting a display image to a windshield of a vehicle or a semitransmissive plate called a combiner. An example of such a display is disclosed in Patent Literature 1. A display device for vehicle 1 is installed in a dashboard of a vehicle. A display light L projected by the display device for vehicle 1 is reflected by a windshield 2, and a vehicle driver 3 can visually recognize a virtual image V superimposed on a landscape (see FIG. 1).
One of such a display device for vehicle is provided with a spatial light modulation element using a field sequential drive system. When a digital micro-mirror device (DMD) or a reflection type display device is used as a spatial light modulation element in a high temperature environment like in a vehicle, if a DMD is driven in a normal temperature environment, there occurs a problem that a mirror of DMD is fixed to a constant state of either ON or OFF, an irreversible bright spot defect occurs, and the life of DMD is reduced. To solve such a problem, the applicant has proposed a display device for vehicle, in which a frame for forming a display image is provided with a display period for displaying an image by driving a light source and DMD, and a non-display period in which a light source is turned on and a DMD is appropriately driven. A DMD is driven during a non-display period, so that an ON drive period and an OFF drive period of each mirror of DMD within a frame becomes substantially equal (Japanese Patent Application No. 2011-210042).